1. Field of Invention
The invention relates to a method and apparatus for removing residue from a substrate.
2. Description of Related Art
Typically, during fabrication of integrated circuits (ICs), semiconductor production equipment utilize a (dry) plasma etch process to remove or etch material along fine lines or within vias or contacts patterned on a semiconductor substrate. The success of the plasma etch process requires that the etch chemistry includes chemical reactants suitable for selectively etching one material while substantially not etching another material. For example, on a semiconductor substrate, a pattern formed in a mask layer can be transferred to an underlying layer of a selected material utilizing a plasma etching process. The mask layer may comprise a radiation-sensitive layer, such as a photo-resist layer, having a pattern formed therein using a lithographic process. Once the pattern is transferred from the patterned mask layer to the underlying layer, using, for example, dry plasma etching, the remaining mask layer, as well as post-etch residues, are removed via an ashing (or stripping) process. For instance, in conventional ashing processes, the substrate having the remaining mask layer is exposed to an oxygen plasma formed from the introduction of diatomic oxygen (O2) and ionization/dissociation thereof. However, the ability to remove residual protective mask layers while maintaining pattern integrity (e.g., CD, roughness, etc.) and minimizing damage to the underlying layer is critical.
Furthermore, during pattern transfer, undulations or variations in the edge profile of the pattern in the mask layer as well as variations in pattern dimension, can be propagated into the underlying layers. These undulations or variations may be observed as edge roughness or line edge roughness (LER) in some instances, or as pitting in other instances. Edge roughness may arise due to damage to the layer of radiation-sensitive material. During the application of the radiation-sensitive material, the post-application bake (PAB), the exposure step, the post-exposure bake (PEB), or the wet developing step, or any combination thereof, the radiation-sensitive material may be damaged. Moreover, damage may occur during the initial phases of the ARC layer etch, hard mask etch, or thin film etch. Pitting may arise when performing pattern transfer in a porous material, such as porous low dielectric constant (low-k) materials or porous ultra-low-k materials.